Re: [GIT PULL] x86/txt for v2.6.32

[Roland Dreier <rdreier@cisco.com>]

 > > > So I modify the RAM content so that BIOS does not think measured
 > > > environment existed before suspend?

 > And it is ridiculously easy to pull off, too:
 > http://www.engadget.com/2008/02/21/cold-boot-disk-encryption-attack-is-shockingly-effective/
 > 
 > Shows the attack being used to read sensitive keys, but you can use it also
 > to *modify* system running state (it will be more difficult, as you need to
 > remove and replace the RAM while on S3 instead of S5, but it should be
 > doable by someone who knows what he is doing).

I believe the whole point of this TXT / S3 handling is that the resume
from S3 will then be able to detect that the contents of RAM have been
modified while the system was asleep.

TXT simply produces a reasonably trustworthy measurement of system
state.  If you modify RAM while the system is asleep, then you will not
be able to produce a measurement showing an unmodified system state.

 - R.